Radio receiver



April 10, 1951 F. s. MABRY ET AL 2,548,383

RADIO RECEIVER Filed Sept. 12, 1946 2 SheeEs-Sheet 1 VENTOR5 WITNESSES:

n Filed Sept. 12, 1946 '2 Sheets-Sheet 2 p 1951 F. s. MABRY ET AL 2,548,383

RADIO RECEIVER INVENTOR5 1 5/7125! 5. MAP 0m Mai $1119 M 0/2. 7

ATTORNE Patented Apr. 1 fl951 UNITED STATES PTENT, OFFICE v I 2 ,548,383, 7 I v 'nAnro RECEIVER Forrest Mabry and William R. Wilson, Balt i more, Md, assignors, by me'sne assignments, to

the United States of America as represented by the Secretary of the Navy Application September 12,1946, Serial No. 696,577

1 Claim. (01. 250-) cuits, and in particular, relates to an improved 7 form of structure and arrangement for such a unit comprising an amplifier, an oscillator and a mixer or intermediate frequency converter useful, for example, in superheterodyne receivers.

In employing circuits for ultra-high frequency waves, such, for example, as those which have come into wide use during thepast few years for radar and communication systems, difiicult problems arise from the distributed inductance and capacitance of theelements of electron tubes and of the lead wires interconnecting such tubes into operative high-frequency circuits. At the frequencies used in ordinary broadcasting the various electron tubes comprised in amplifiers, superheterodyne circuits and the like can readily be located suflficiently close to eachother, without the necessity for unusualstructural arrangements, so that the distributed inductance and capacitance of the lead wiresinterconnecting the tubes is negligible compared with the lumped in ductances and capacitances employed in the circuits. However, assets are designed for higher and higher frequencies, a; stage is reached when the distributed ind-uctances and capacitances of the interconnecting lead wires become substantial, and even controlling compared with the lumped capacitances and inductances required to tune the resonant circuits at the frequencies involved. Moreover, the size of the lumped inductances and capacitances constituting the resonant circuit grows smaller and smaller, and the-stray power radiated and lost from them grows larger and larger so that it becomes necessary to abandon the use of conventional inductors and capacitors familiar in broadcasting frequencies and to substitute, for the ordinary tuned circuits, resonant chambers of one type or another. Small sections of concentric transmission lines, that is to say a central conductive core surrounded by a conducting sheath, constitute a type of resonant chamber which has numerous advantages for many purposes.

Likewise, the electrode capacitance of conventional broadcasting tubes is so great that at ultrahigh frequencies they cannot be used without difficulty, and as a result, a particular'type of electron tube structure, quite different from the conventional broadcasting electrontubes, and commonly called the lighthouse tubehas come into Wide use. c

In view of all the foregoing considerations, the design of a supporting and shielding structure in which electron tubes may be desired circuits, such asthe heterodyning circuit employing anR. F; amplifier, an oscillator and a mixer or I. F. converter, analagous to. similar circuits widely employed at broadcasting. frequencies is a problem of considerable difiiculty.

One object of our invention is, accordingly, to

provide a supporting and shielding'structure in which three ultra-high frequency electron tubes may be operatively connected into a heterodyning circuit comprising an amplifier, an oscillator and a mixer or I. F. converter.

Another object of our invention is to provide an arrangement in which ultra-high frequency tubes are supported in a unit structure comprising chambers which perform the dual function of resonators and shields capable of preventing the loss of substantial amounts of ultra-high frequency power stray radiation. 9 I

Still another object of our invention is to provide a structure comprisinga plurality of conducting metal chambers Which may be conveniently and cheaply produced by die casting and Which-supports and interconnects a plurality of ultra-high frequency radio tubes in an operativecircuit relation; I

Still anotherobject of our invention is to'provide an enclosing structure comprising a plurality of chambers which support and interconnect ultra-high frequency radio tubes for operation,

but which are so constructed asfto make the radio Fig. 4 isa sectional view taken along the line IVIV in Fig; 1.

Referring to thedrawings in detail, I, 2 and 3 are three ultra-high frequency electron tubes 1 of a type commonly known as -l ighthouse tubes," which are to be connected, together for heterodyningand amplifying ;purposes; I acting as an oscillation generator ;;',2 a mixer or converter; and 3 as an amplifier of incoming'power. We have diagrammatically shown in each of these tubes an-anodeJE, a control "electrode .6, a unioperated in certain potential cathode I and a heater filament 8 therefor by symbols conventional in the art, it being understood that these are symbolic rather than structurally representative of the internal arrangements of the lighthouse tubes. Each -lighthouse tube does, however, have the general external appearance shown at I comprising an insulating base 9 supporting a cylindrical metallic sleeve II which is connected capacitively to the unipotential cathode I and which supports a shock-glass cylinder I2, which, in turn, supports a metal rim I3 attached to the control electrcdefi. The rim I3 in turn supports a second glass cylinder I4 capped at its upper end by a metal plate l5 which is connected to the anode 5 and is provided with a cylindrical extension or cap I6 adapted to make contact with inleading conductors in a manner well known in the tube art. v

The base 9 fits into a socket ll of insulating material, which, in turn, is, fastened into a cuplike cap I3 of sheet metal. The tube I, socket I7 and cap I8 constitute, when assembled, a unitary structure which can be handled and removed as a unit from the remainder of the structure inthe manner of the supporting chamber of Fig. 1.

- The supporting structure embodying the main features of my invention comprises a die-cast metal envelope 2I divided into three adjacent chambers by integral metal walls 22 and 23. The floor of each chamber is formed by an integral wall 24 which is provided with suitable central openings through which may pass the inleading conductors to the anode of the oscillator I and amplifier 3, and through which projects the lower part of the tube 2 in a manner to be described in more detail later.

As is evident from Figs. 3 and 4, the rear wall of the chambers 2|, 22 and 23 is a continuous integral metal plate 25. The top of the respective chambers is likewise formed by a metal plate 26 cast integral with the structure so far described and provided over the center of each chamber with openings through which may project the tubes I and 3, andthe support'for the tube 2 in a manner to be described in more detail later.

The front of the three chambers above described is arranged to be closed by a continuous metal plate 21 adapted to be removably held in place by screws threaded into'the holes23 inth'e' side walls 2|, 22 and 23 of the chambers. As'will be described in more detail below, the removable wall 21 is arranged to support adjustable tuning members which form tuning capacitors with parts of the tubular members centrally positioned within the chambers.

As was previously stated, the tubes I, 2 and 3 together with their caps which are removably supported constitute removable units which may be taken out of the electrical circuit for inspection or the like. In order to hold them securely in place when in use, we provide resilient members 3|, each of roughly U-form and supporting a small roller 32. The members 3I are of resilient wire provided with spring-forming loops 33 and havingv their ends threaded through holes in' ears 34 which are fastened to the top plate 26. The members 3! are so proportioned that when the tubes I, 2 and 3 are'in proper position in the three chambers above mentioned, the rollers '32 are pressed downward on the tops of the caps I8 and exert a downward pressure on the'tubes I and the caps I8 in which they are pressed. When it is desired to remove any oi the tubes I, 2 and 3 for inspection, the upper ends of the members 3| are moved in a direction corresponding to the plane of the shape in Fig. l, rotating about the projecting ends which pass through holes in the members 34 until the caps I8 are relieved from contact with the rollers 32. The tubes I, 2 and 3 may then be removed at will; and when returned to position within the chambers, the members 3| are again turned to bring the rollers 32 over the center of the top of the caps I8 thereby again exerting a downward pressure on the latter and the tubes I, Zand 3 which they support.

The cap I6 of tube I is pressed downward into a flexible clasp, or plate contact, 35 which is attached to the upper end of a metallic tube, or plate line, 33 having its base attached to the bottom plate 24. The tip of the contact 35 is in the form of a cylindrical plug and is seated in a circular recess in a semi-circular metallic pad I00. The "pad rests on one plate of an angle "I2, the

other plate of which extends parallel to the contact 35. The pad is insulated from the angle I2 by a mica strip I03. The assembly consisting of the contact 35, pad I30, mica strip I03 and angle 12 are held together by a screw I05, the head of which engages an insulating washer I31 and the threaded end of which engages the tip of the contact, pressing the washer against the angle '52. A clearance hole is provided in the angle plate 32 so that the screw remains insulated from the latter. The condenser formed between pad H30 and angle 12 constitutes a by-pass capacity to the plate line 36. I

Inside the tubular plate line 36 are located a resistor 31 connected at its upper end to the contact 35 and connected at its lower end to a line conductor which is passed through a feedthru type by-pass capacitor H3 in the bottom plate 24. After passing through the bottom plate 24, the lastementioned lead wire is connected through a resistor 33 to the positive terminals of a source of direct current voltage of which the negative terminal is connected to the walls 2 I, 22

and 23. r a

A biasing resistor 4| in parallel with an R. F. by-pass capacitor 42 is connected between cathode I and ground (the grounded shell of the tube base). Heating current for the filament 8 is supplied through an R. F. choke 43 both terminals of which are by-passed to ground (shell of the tube base) by capacitors 45 and III respectiyely. The components M, 42, 43, 45 and III are supported on the terminals of tube socket I'I which projects into the cap I8.

Contact is made between the cylinder wall portion of the tube I and the top plate 26 by a series of flexible metal fingers 48. Contact is likewise made from the metal plate I3 which is connected to the control electrode 6 by a flexible metal finger 41 which is supported on the wall 2 I but insulated therefrom by a mica plate 48. The finger 41 and the mica plate are held in position against the wall 2I by a machine screw 49 separated from the finger 4'! by an insulator SI having on its outer surface a terminal washer 52. The terminal washer 52 is connected to the wall 2I by the machine screw 49 and is likewise connected to one end of a resistor 53, .the other end of which is connected 'to the finger 41. The members 47, 43 and 53 will be seen to constitute a grid leak and condenser intervening between the control electrode 3 and the grounded caschamber will resonate may"bea djustedfi T e, annular, spa e een th u e serfa of the cylinder- 3 6 and the interiorflsurf'ace f of i cillat'ingvoltages,induced'in it from the tube I having its ends tubeI'atthenpper erid of the chamber andthe other end of'this'inductance-being connected to it the anode of the tube I. 'The'machinescrew lfl -"in effect connects an intermediate point on this inductor with the control'grid 6 of the' tub-e' l s iib above. The"circuitarrangernent;thuspro is, in effect, anoscillator probably of the tr time type will cause the'tube Ito generate throughthe grid leak and' condenser' oscillations at a frequency ideterminedfby' the tube I is' located. Y

The frequency at which the above-mentioned {accor'dan'ce-"with the principles'well known-fin; the

20.1 atin onstants of'the chamber in which {the 1 art, byshunting a variable capacitor between'the 'central corefifi and the walls of the chamber;2 I. 'An angle-Ifattached to the" upperend of the central cylinder 36 is adapted to act as'one plate of such a condenser and a cooperating plate may be supported on a screw threaded through the front plate 2I', thisscrew being moved in and out to change the gap between the angle 12 and its associated plate, thereby varying the capacity of the" shunting condenser between the upper end of the cylinder 36 and the walls of 'the chamber;

The metal chamber between the Walls .22 and 23 is provided with a'downwardly projecting rhetalcylinder El attached at'its upper endto the top plate 25 and projecting now down to the floor plate 24. Inside the cylinder 5| is positioned a secondcylinder "52 which projects through a hole in the top plate 26 and is connected to the cap I8. At its lower end the cylinder 62 supports an insulating base II similar to that already described in connection with'tube I, and this base acts as a socket for the'tube 2.

This socket contains a'similar arrangement of resistor H5 and capacitors 42, and III and inductor 43 to that already described in connection with tube I except that the ungrounded terminal of the filament 8 is connected to an inductor 56 and a lead 51 to the same terminal of the source of heating current as is the conductor M.

The control electrode 6 of the tube 2 is connected through the metal plate I3 of the tube 2 and a set of flexible contact fingers 63 to the floor plate 24. The anode cap I6 is adapted to be connected by any suitable means well known in the art through a resistor 64 to the positive terminal of a voltage source of which the negative terminal is grounded and connected to the metal walls of the assembly.

' The cylinder SI constitutes in effect an impedance intervening between the cathode I and the control electrode 6 of the tube 2 which is connected by means of fingers 63 to the grounded top plate 26 of the chamber containing the cylinder BI. A conductor 65 has one end connected to a suitable point on the cylinder 6| and passes through an insulator 6B in the wall 22 to form a loop having its other end connected to the Wall 22. The loop just mentioned ispositioned in the resand its cavity are impressed on the cathode impedance of tube '2 which is constituted bythe cylinder 6|. 7 v p A conductor 6? is connected to another suitable point on the cylinder 6% and-leadsfthrough'an insulated concentric cable 68 into the chamber containing tube 3'.

Tube 3 is removably supported Within its enclosing chamber from a cap I8 just as has already been described for tube I. The cathode circuit'of tube 3 is likewise connected to thetop plate,26 by flexible metal fingers IB similar to those described in connection with tube I I. The cathode connections of tube 3 are precisely similar to those'already'described in connection with tube I so that a repetition of this description here is unnecessary. The cap I6 of tube 3 is slip- "on the u per end of a tubular cylinder fl I'having f the same manner as is the cap I6 of tube Ifl'lhe I anode of tube 3 is connected to the terminal of an external voltage source in the same way as has been described for the" anode of tube I and, the description need not be given in detail here. [The upperfend of the cylinder II is provided with an angle "I2, the verticalleg of which is adapted. to cooperate with a movable plate I3 to form a'tuned I capacitor as shown in more detail in Fig. 4. I

The control electrode 5 of'tube 3 is connected throughits plate I3 and a set of flexible fingers 14 to the upper end of a metal tube I5, the lower end of which is connected to the flooiypl'ate 24.

The annular space between the tubesll and la constitutes aresonant cavity interc'o' r'in'ectingthe jlfig. 1, this cavity 'may'have its resonahtfrquency varied by the adjustable condenser comprising the members I2 and I3 showninFigA. The plate I3 is supported by a threadedflscrew on the tube I5, this screw passing. through a hoie "in thefront plate, 2I. .f

Thean'nular space between the cylinderldand the interior walls of chamber cont'ainingtube S constitutes a cavityjresonatorfbetween the cathode and grid of th'e tube ,3. )AsisdshoWh more clearly in ,Fig. .4, the tilbellfi' 'is m/id a at its upper end' with a' flat pl'atelfi which cooperates with a movable plate I? supported on a screw threaded through the cover plate 2?. By adj'usting the position of the plate II, it is possible to tune the cathode to grid cavity resonator above mentioned.

The tube II constitutes, in effect, an impedance in the plate circuit of the tube 3 and the conductor 6! is connected at one end to a suitable point on the impedance. This conductor, accordingly, impresses voltage of the frequency present in the amplifier tube 3 on a point in the cathode impedance of the mixer or converter tube 2.

Incoming ultra-high frequency signals are impressed on the grid circuit of tube 3 by means of a conductor I8 which passes in coaxial cable through the floor plate 24 and is tapped at a suitable point to the grid-cylinder I5. A moments consideration will show that where an incoming signal is impressed on the grid of the amplifier tube 3 by the conductor I8, this tube will act as an amplifier and the voltage in its plate circuit comprising'cylinder II will be impressed by conductor 61 on the cathode line of tube 2. The conductor 65 picking up voltage of the frequency being generated by the oscillator ported by a'fiexible clasp or plate contactfifi tube I will impress the latter frequency likewise on the cathode line of the mixer tube 2. The result of this will be in the plate circuit of the mixer tube 2, a voltage having, among other frequencies, the difierence-frequency of the amplifier 3 and the oscillator. A suitable outgoing network filtering out the other (undesired) frequencies connected to the anode of tube I6 may be used to impress this difierence-frequency on any other desired apparatus. For example, this difference-frequency may be impressed on the intermediate frequency amplifiers of a superheterodyne receiver.

In an R. F. assembly in accordance with our invention which we have found to operate satisfactorily, the tubes I, 2 and 3 are all lighthouse tubes" type 2040.1. A2046 tube would also operate satisfactorily. Capacitors 42, 45, I H and H3 are all 470 mmf. Resistors 31, 38 and 53 are 1000 ohms each, resistor 4| is 560 ohms, resistor l is 2200 ohms, resistor 64 is 47,000 ohms. The chokes '43 are resonant at 60 1110., the I. F. The lines and cavities are approximately of the dimensions shown in the drawing, and may be scaled from the drawing. The mica strips I03 and 48 are approximately .005 inch in thickness. The anode-cathode potential for tubes l and 2 is relatively low of the order of 100 volts. The anode-cathode potential for tube 3 is of the order of 200 volts. The R. F. head operates satisfactorily at 500 to 560 megacycles but with properly dimensioned lines and cavities will operate at other frequencies.

Because of the compact and integral construction above described, the stray capacitance and inductance of the leads interconnecting the tubes is reduced to a minimum. On the other hand, the tubes l, 2 and 3 are readily accessible and easily removed and the entire structure can be produced very cheaply and economically by diecasting processes.

We claim as our invention:

A supporting structure for tubes constituting an oscillator, an amplifier and a mixer or converter in a high frequency circuit comprising a conductive enclosure subdivided by conductive walls into three chambers, an electron tube having a cathode, anode and a control electrode supported within the first of said chambers with its cathode connected to the top wall thereof by removable connectors, said control electrode being connected to an intermediate point on said chamber wall through a suitable impedance, and said anode being connected to a central conductor extending upward from the floor of its containing chamber, a mixer tube having a cathode, anode and control electrode, supported within said second chamber by a central tubular conductor having its upper end connected to the top wall of said second chamber, the control electrode of said mixer tube being positioned adjacent the floor of said second chamber and connected thereto, an amplifier tube having. a cathode, anode and control electrode, supported within the third chamber with its cathode removably connected to the top wall thereof and its anode connected to a tubular conductor projecting upward from the floor of said third chamber, a tubular conductor having its lower end connected to the floor of said third chamber and its upper end removably connected to the control electrode of said amplifier tube, a conductor extending from a point on the anode conductor of said amplifier tube to a point on the cathode conductor of said mixer, and a second conductor extending from a point on the cathode conductor of said mixer into inductive relationship with the interior of said first chamber.

FORREST S. MABRY.

WILLIAM R. WILSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,266,500 Lindenblad Dec. 16, 1941 2,277,638 George Mar. 24, 1942 2,411,424 Gurewitsch Nov. 19, 1946 2,415,977 Turner Feb. 18, 1947 2,416,567 McArthur Feb. 25, 1947 2,429,811 Guarrera Oct. 28, 1947 2,436,398 Morton Feb. 24, 1948 2,457,997 George Jan. 4, 1949 2,462,866 Hotine Mar. 1, 1949 2,474,608 Wheeler June 28, 1949 

